1. Field
A scroll compressor is disclosed herein.
2. Background
In general, a scroll compressor is widely used for refrigerant compression in an air-conditioning apparatus, for example, as it is capable of obtaining a relatively higher compression ratio than other types of compressors, and acquiring a stable torque resulting from smooth strokes of suction, compression, and discharge of the refrigerant. A behavior of the scroll compressor is dependent on shapes of a fixed wrap and an orbiting wrap. The fixed wrap and the orbiting wrap may have a random shape, but typically they have a shape of an involute curve, which is easy to manufacture.
The term “involute curve” refers to a curve corresponding to a track drawn by an end of a thread when unwinding the thread wound around a basic circle with a predetermined radius. When such an involute curve is used, the wrap has a uniform thickness, and a rate of volume change of a plurality of compression chambers is constantly maintained. Hence, a number of turns of the wrap should increase to obtain a sufficient compression ratio, which may, however, cause the compressor to be increased in size corresponding to the increased number of turns of the wrap.
The orbiting scroll typically includes a disk, and the orbiting wrap is located on one side of the disk. A boss having a predetermined height is formed at a surface of the disk opposite to the side at which the orbiting wrap is formed. The boss is eccentrically connected to a rotational shaft, which is coupled to a rotor of the motor, so as to allow the orbiting scroll to perform an orbiting motion. Such an arrangement allows the orbiting wrap to be formed on almost an entire surface of the disk, thereby reducing a diameter of the disk for obtaining a uniform compression ratio. However, as the orbiting wrap and the boss are spaced from each other in an axial direction, a point of application of a repulsive force of a refrigerant applied upon compression and a point of application of a reaction force, which is opposed to the repulsive force of the refrigerant, are spaced apart from each other in the axial direction. Accordingly, the repulsive force and the reaction force are applied to each other as a torque during operation of the compressor. This causes the orbiting scroll to be inclined, thereby generating more vibration and noise.
To solve this problem, for example, Korean Patent Registration No. 10-1059880, which is incorporated herein by reference, introduced a scroll compressor in which a coupled portion between a rotational shaft and an orbiting scroll is located on a same plane as an orbiting wrap. This type of scroll compressor can solve the problem that the orbiting scroll is inclined because a point of application of a repulsive force of a refrigerant and a point of application of a reaction force against the repulsive force are opposed to each other at a same height.
In the scroll compressor, as only one discharge port to discharge a refrigerant compressed in each compression chamber is provided, a refrigerant compressed in a first compression chamber formed on an outer surface of the orbiting wrap and a refrigerant compressed in a second compression chamber formed on an inner surface of the orbiting wrap are discharged through the one discharge port.
However, when the one discharge port is provided, it may be easy to design a same discharge time point for both compression chambers only when the discharge port is located at a center of a compression unit or device. However, in a scroll compressor having a structure that the rotational shaft overlaps the orbiting wrap in a radial direction, the rotational shaft is located at a central portion of the orbiting scroll, and thereby the discharge port is located eccentric from the center of the compression device. Accordingly, as illustrated in FIG. 1, a time point of opening a discharge port DP for a first compression chamber S11 and a time point of opening the discharge port DP for the second compression chamber S12 are different from each other, whereby an over-compression loss due to a delayed discharge is brought about in a compression chamber from which a refrigerant is discharged relatively late.
Also, in the scroll compressor having the structure that the rotational shaft overlaps the orbiting wrap in the radial direction, even though the second compression chamber S12 has a higher compression ratio than the first compression chamber S11, the second compression chamber S12 is opened later than the first compression chamber S11 or has a same discharge area as the first compression chamber S11. This results in a further increase in over-compression loss in the second compression chamber S12. In FIG. 1, unexplained reference numeral 32 is a fixed scroll, while unexplained reference numeral 33 is an orbiting scroll.